Nov. 27 (UPI) -- Neanderthals' thumbs stuck out from their hands at a much wider angle than humans, making it easier to grip certain tools, according to a study published this week.
The paper, published Thursday in Scientific Reports, said Neanderthals were well-adapted to grip tools the way we grab hammers -- but would have struggled to hold a pencil or shake hands with someone else.
Ameline Bardo, a postdoctoral research fellow at the University of Kent's School of Anthropology and Conservation in the United Kingdom, used a 3D analysis to map the hands of five Neanderthal individuals and compared them to five early modern humans and 50 recent modern adults.
Bardo analyzed the set of joints responsible for the thumb -- called the trapeziometacarpal complex -- and found Neanderthals would have struggled with precision grips, where objects are held between the tip of the finger and the thumb.
But the Stone Age people, who went extinct about 40,000 years ago, were well-suited to the "squeeze grip" modern humans use when grabbing a hammer.
"The joint at the base of the thumb of the Neanderthal fossils is flatter with a smaller contact surface between the bones, which is better suited to an extended thumb positioned alongside the side of the hand," Bardo told CNN. "This thumb posture suggests the regular use of power 'squeeze' grips."
While other researchers have studied how thumb bones vary in Neanderthals, most research has looked at the bones in isolation and hasn't analyzed how the different bones, joints and ligaments relate to one another.